Communication systems allow information to be transmitted from one location to another via a communication medium. The communication medium may be bounded, such as a wireline medium, or unbounded, such as a wireless medium. A communication system can include (1) a transmitter that modulates information onto a carrier wave and transmits it on the communication medium and (2) a receiver that receives the carrier wave and demodulates the signal to obtain the information. Various signal processing techniques can be used to modulate information onto a carrier wave and demodulate the signal to obtain the information.
Some such techniques include modulating and demodulating digital information. An example of a technique for modulating and demodulating digital information is multiple frequency-shift keying (M-FSK). M-FSK is form of frequency-shift keying (FSK). FSK is a method for transmitting digital information in which a waveform at a first frequency represents digital 0 and a waveform at a second frequency represents digital 1. M-FSK utilizes two or more tones to transmit the digital information. Another technique for modulating and demodulating digital information is orthogonal frequency division multiplexing (OFDM). OFDM is a method for transmitting digital information in which a relatively large number of orthogonal sub-carriers are modulated at a relatively low symbol rate. OFDM offers the ability to use many slowly modulated narrowband signals to transmit data even when conditions in the communication medium and channel are undesirable.
These and other modulation techniques may be demodulated and/or analyzed using a Fast Fourier Transform (FFT) algorithm. The FFT algorithm can be used to measure frequency of a signal by measuring the magnitude, or the amount of energy, within a signal and/or samples of a signal. A channel that provides the highest magnitude indicates a value of the signal frequency, and thus a value for the data being transmitted.
Some communication systems utilize two or more different modulation techniques to support data communication. A receiver may receive two or more data signals from one or more transmitters, where each data signal is modulated using different modulation techniques. For example, one data signal may be modulated using an M-FSK modulation technique and a second data signal may be modulated using an OFDM modulation technique. Some communication systems provide the capability of receiving signals simultaneously. Conventional receivers require several components to perform demodulation techniques on two data signals received at the same time. Furthermore, some conventional receivers require separate components to perform demodulation on data signals modulated using different modulation techniques, even requiring multiple demodulators and FFT components to determine a frequency or magnitude. Some receivers experience difficulty in simultaneously receiving and processing a plurality of signals transmitted using the same modulation technique. Accordingly, systems and methods are desirable that can process signals without requiring such additional components.